BBP bags may look like an ordinary messenger bag you find anywhere, but they are a bit different. The bak2pak carrying system they’ve trademarked is designed so that you can carry it over one shoulder like standard messenger bags, or backpack style over two shoulders. From the pictures on their site, it looks like the backpack way is worn low to me. If you are interested in more, they h ave a video and animation showing exactly how to make the switch from one shoulder to two shoulder.